This slight disagreement between datasets is known as tension in the model. There have been various proposed solutions to easing this tension, such as factoring in neutrino mass, but in this new work the authors propose resolving it by connected dark matter and dark energy. To do this they tweaked the ΛCDM model slightly. The Λ or “lambda” in ΛCDM represents the cosmological constant that drives dark energy. The CDM stands for “cold dark matter,” which is the leading model for dark matter. In the standard cosmological model these two are separate and constant, but the authors proposed that dark matter could decay into dark energy (by some unknown process) so that over the history of the universe the Λ would increase while the CDM decreased. The decay of one into the other would be slow, but the authors found that such a decay would ease tension in the observational data.

It should be pointed out that this doesn’t prove such a decay occurs, only that tweaking the standard model in such away seems to better fit the data. Tweak theories are weak theories, as I’ve said before. But what this new work does show is that modifications of the standard model are something worth exploring. As we strive to solve the mysteries of dark matter and dark energy, they may turn out to be two sides of the same coin.